Vibrio cholerae tolC is required for bile resistance and colonization

Abstract

TolC and its homologues are outer membrane proteins that are essential for the transport of many molecules across the cell envelope. In this study we characterized the gene encoding Vibrio cholerae TolC. V. cholerae tolC mutants failed to secrete the RTX cytotoxin, were hypersensitive to antimicrobial agents, and were deficient in intestinal colonization.

FIG. 1

Cytotoxicity of V. cholerae N16961Sm-tolC::pM2436 on tissue cultured HEp-2 cells. Subconfluent HEp-2 monolayers were exposed for 90 min to PBS-washed V. cholerae cells at a multiplicity of infection of 100. V. cholerae strains added were N16961Sm (A), mock (PBS) (B), N16961Sm-tolC::pM2436 (C), and N16961Sm-ΔrtxA (D).

FIG. 2

Effect of bile salts on relative growth rates of N16961Sm and N16961-ΔtolC. The relative exponential growth rates of N16961Sm (open circles) and N16961-ΔtolC (open squares) at 37°C in LB broth containing various amounts of bile salts are shown. The reported growth rates were normalized to the growth rates of the respective strains in the absence of bile salts.